The present invention relates in general to multi-colored material, and more particularly, to decorative multi-colored images formed from rainbow gratings which simultaneously evidence a plurality of different colors having enhanced color separation.
Ruling and rainbow gratings are known materials which reflect a wide range of spectral colors. The common names of the observable pure spectral hues for the several wave length ranges are violet at between 3900-4550 angstroms, blue at between 4550-4920 angstrom green at between 4920-5770 angstroms, yellow at between 5770-5970 angstroms, orange at between 5970-6220 angstroms and red at between 6220-7700 angstroms. The different colors of the spectrum are observed by viewing surface portions of the grating at different angles of the incident light rays. Accordingly, by tilting the rainbow grating about its planar axis, the spectral colors of violet, blue, green, yellow, orange and red are subsequently observable.
Ruling gratings have been made by a number of methods over the years. Historically, a metal cylinder having a polished planar surface was processed in what was commonly referred to as a ruling engine. The ruling engine would inscribe the polished planar surface with a continuous groove having a resolution of approximately 1600 lines per inch. The resulting inscribed surface would be plated with a metal layer, for example, nickel, which upon removal from the inscribed surface would have one surface forming the grating. As the construction of a grating from a ruling engine was quite time consuming and expensive, an alternative method for producing a grating was developed.
In a rainbow grating, a glass master plate having a photo emulsion is inscribed by photographic means with the corresponding image of the rainbow grating, i.e., grooves, previously formed by the ruling engine. The use of photographic techniques was found to enhance the resolution of the rainbow grating by providing for a higher resolution of approximately 2400 lines per inch. Master plates of this type are available from Steve Provence Holography of Boulder Creek, Calif., Lasersmith of Chicago, Ill. and Light Impressions of Santa Cruz, Calif. The master plate is used to form a rainbow grating by plating a layer of nickel over a conductive silver layer from a suitable plating emulsion. The procedures for forming a rainbow grating by plating techniques from an emulsion are known from the manufactures thereof, i.e., using standard metal emulsion plating techniques and will not be described herein.
The resulting ruling or rainbow grating from either of the aforedescribed techniques have been used in similar ways to form decorative foils and the like. For example, a portion of the grating has been overlayed onto a die to form a repetitive pattern on the metalized surface of a polymer film. The resulting material has been decoratively used for wrapping of packages, lamination for miscellaneous products, labels and the like. Typically, the repetitive patterns have been geometric shapes, each portion of which evidencing identical color change upon change of the angle of incident of light to the viewer. Although these known techniques for the use of gratings have enhanced the use of decorative polymer films, such techniques have been limited in their ability to take advantage of the multiple color capability which these gratings evidence. To this end, the present invention provides decorative multi-colored materials using rainbow gratings which evidence independent color change so as to provide multiple color images to enhance the decorative nature and to extend the aesthetic utility of these materials.